The published patents GB2173472 (which patent family disclosed as EP0200369, U.S. Pat. No. 4,790,718), SE8502327 (which patent family disclosed as U.S. Pat. No. 4,732,525) and EP0674969 (which patent family disclosed as U.S. Pat. No. 6,336,375) have disclosed a hybrid robot, which comprises a three degree-of-freedom parallel mechanism and a two degree-of-freedom wrist connected in series to the parallel mechanism. The parallel mechanism includes three driving length adjustment devices that are stretchable in an axial direction, wherein one end of each of the driving length adjustment devices is connected to a rack through a two-degree-of-freedom hinge, while the other end thereof is connected to a moving platform through a three-degree-of-freedom hinge; a driven length adjustment device is further provided in this structure, with one end being fixedly connected to the moving platform while the other end being connected to the rack through a two-degree-of-freedom hinge. However, in such a robot, as the hinges of the driving length adjustment devices connected to the moving platform are three-degree-of-freedom hinges and each of the driving length adjustment devices is connected to a rack through a two-degree-of-freedom hinge, the structure is complicated in the mechanism.
Patent CN102699899A disclosed an over-constrained hybrid robot, which also comprises a three degree-of-freedom parallel mechanism and a two degree-of-freedom wrist connected in series to the parallel mechanism. The parallel mechanism includes three driving length adjustment devices that are stretchable in an axial direction, and a driven length adjustment device, wherein two of the driving length adjustment devices are connected to a moving platform through single-degree-of-freedom hinges and symmetrically arranged on left and right sides of the driven length adjustment device such that they are placed in the same plane; and, the other one of the driving length adjustment devices is connected to the moving platform through a three-degree-of-freedom hinge and arranged below the driven length adjustment device. This robot reduces number of single-degree-of-freedom hinges, but requires strict manufacture and mounting accuracy due to the over-constrained structure. In addition, each length adjustment device is connected to a rack through a two-degree-of-freedom hinge, respectively, so the structure is complicated and the manufacturing process of the rack is relatively complicated.
Patent CN1212221C disclosed a four-degree-of-freedom hybrid robot, which comprises a parallel mechanism with two degrees of freedom and a two-degree-of-freedom wrist connected in series to the parallel mechanism. However, the parallel mechanism only can realize a planar motion.